Core structure of heat exchanger

ABSTRACT

A core structure includes a plurality of flat tubes and a plurality of corrugated inner fins. Each corrugated inner fin has top portions for being fixed to an inner surface of an upper wall portion of the tubes, bottom portions for being fixed to an inner surface of a lower wall portion thereof, and slanted portions for connecting the top portion with adjacent bottom portions thereof. The corrugated inner fin has first corrugations located at both end sides of the corrugated inner fin and second corrugations located between the first corrugations, where the first and the second corrugations has the top portion and the adjacent slanted portions and project from the bottom portions. The first corrugations are set to be smaller in a front-back directional length of the corrugated inner fin than a front-back directional length of the second corrugations.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a core structure, of a heat exchanger,which has a plurality of flat tubes each containing a corrugated innerfin in a state where the inner fin is fixed to an inner surface of theflat tube.

2. Description of the Related Art

A conventional core structure of a heat exchanger of this kind isdisclosed in Japanese Utility Model laid-open publication No.(Jikkaisyo) 59-148978, Japanese Patents laid-open publication No.(Tokkaihei) 07-265985, No. (Tokkkaihei) 08-71836, No. (Tokkaihei)09-229578, and No. 2004-061032. These conventional core structures havea plurality of flat tubes and corrugated inner fins contained in theflat tubes and fixed to their inner surfaces by brazing. The flat tubeshas an upper flat wall portion, a lower flat wall portion arranged inparallel to the upper flat portion, a first arc wall portion continuedto connect one end portions of the upper and lower wall portions, and asecond arc wall portion continued to connect the other end portions ofthe upper and lower wall portions, and are integrally formedhorizontally long and vertically short.

These flat tubes and corrugated inner fins of the conventional corestructure are manufactured as follows.

The flat tubes and the corrugated inner fins are formed by pressworking, respectively. In this formation, the vertical length of thecorrugated inner fin is formed to be slightly longer than the verticallength between the inner surfaces of the upper and lower flat wallportions of the flat tube. Then, the corrugated inner fin is insertedinto the flat tube, and the upper and lower wall portions of the tubeare pressed from above and below so that top portions and bottomportions of the corrugated inner fin can be close contact with the upperand lower surfaces of the flat tube. The corrugated inner fin and theflat tube are brazed with each other in a state where they are kept tobe close contact therewith.

On the other hand, recently, there is an attempt to form thickness thecorrugated inner fins to be thinner so as to decrease their weights anddrag force of heat transfer medium flowing along the corrugated innerfins in the flat tubes. The thinner corrugated inner fins, however,encounter a problem in that they tend to cause compressive buckling orbe improperly tilted when the press working of the flat tubes containingthe corrugated inner fins. This provides faulty brazing between thecorrugated inner fins and the flat tubes. We have found that thesecompressive buckling and improper tilt in the press working causeespecially at top portions and/or bottom portions of the both end sidesof the corrugated inner fins.

In addition, there is an attempt to decrease thickness of the wallportions of the flat tubes to be also thinner so as to decrease theirweights, ensuring compression strength thereof.

It is, therefore, an object of the present invention to provide a corestructure of a heat exchanger which overcomes the foregoing drawbacksand can improve compressive strength of a corrugated inner fin to beprevented from causing compressive buckling and/or being improperlytilted when a flat tube containing the corrugated inner fin is pressedfrom above and below, so that the corrugated inner fin and the flat tubecan be surly brazed with each other.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is providedan inner fin adapted for a heat exchanger core structure of a heatexchanger where a core part is arranged between a pair of tanks. Thecore structure includes a plurality of flat tubes having an upper wallportion and a lower wall portion; and a plurality of corrugated innerfins formed in a corrugated shape so that each corrugated inner fin hastop portions for being fixed to an inner surface of the upper wallportion, bottom portions for being fixed to an inner surface of thelower wall portion, and slanted portions for connecting the top portionwith adjacent bottom portions thereof. The corrugated inner fin hasfirst corrugations located at both end sides of the corrugated inner finand second corrugations located between the first corrugations, whereeach of the first and the second corrugations has the top portion andthe adjacent slanted portions and project from the bottom portions. Thefirst corrugations are set to be smaller in a front-back directionallength of the corrugated inner fin than a front-back directional lengthof the second corrugations.

Therefore, the core structure of the invention can improve compressivestrength of the corrugated inner fin to be prevented from causingcompressive buckling and/or being improperly tilted when the flat tubecontaining the corrugated inner fin is pressed from above and below, sothat the corrugated inner fin and the flat tube can be surly brazed witheach other.

Preferably, the corrugated inner fin has at least one third corrugationwhich is smaller in the front-back directional length than the secondcorrugations and arranged between the second corrugations.

This can improve the entire strength of the flat tube containing thecorrugated inner fin, keeping a thickness of the corrugated inner fin tobe thinner.

Preferably, the number of the third corrugations located at a front sideof the corrugated inner fin are larger than the number of the thirdcorrugations located at a rear side of the corrugated inner fin.

This can improve a heat transfer efficiency when heat transfer mediumflows through the core part of the heat exchanger.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects, features and advantages of the present invention willbecome apparent as the description proceeds when taken in conjunctionwith the accompanying drawings, in which:

FIG. 1 is a front view showing a condenser having a core structure of afirst embodiment according to the present invention;

FIG. 2 is a rear perspective view showing the condenser shown in FIG. 1;

FIG. 3 is an enlarged side perspective view showing the flat tubecontaining the inner fin of the first embodiment;

FIG. 4 is an enlarged side perspective view showing the inner fin of thefirst embodiment;

FIG. 5 is an enlarged side view showing the inner fin of the firstembodiment, taken along a line S5-S5 in FIG. 4;

FIG. 6 is a schematic diagram showing how to manufacture the inner finof the first embodiment;

FIG. 7 is a plan view showing an upper rotating roller that has teethfor forming the inner fin of the first embodiment;

FIG. 8 is a plan view showing a lower rotating roller that is arrangedunder the upper rotating roller and has teeth for forming the inner finof the first embodiment together with the upper rotating roller;

FIG. 9 is a perspective view showing the flat tube and the inner finshown in FIGS. 4 and 5 before the inner fin is inserted into the flattube;

FIG. 10 is a perspective view showing the flat tube and the inner fincontained in the flat tube before the flat tube is pressed in its heightdirection for brazing the tube and the inner fin,

FIG. 11 is a side perspective view showing an inner fin, contained in aflat tube, used in a core structure of a second embodiment according tothe present invention;

FIG. 12 is a side perspective view showing the inner fin of the secondembodiment; and

FIG. 13 is a side view showing an inner fin used in a core structure ofa third embodiment according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Throughout the following detailed description, similar referencecharacters and numbers refer to similar elements in all figures of thedrawings, and their descriptions are omitted for eliminatingduplication.

A core structure, of a heat exchanger, of a first preferred embodimentaccording to the present invention will be described with reference tothe accompanying drawings. Incidentally, in the following description,terms “right ” and “left” are used with respect to those of a motorvehicle body, not with respect to those of the drawings.

Referring to FIGS. 1 and 2 of the drawings, there is shown a condenser Chaving a core part 3 of the first embodiment of the present invention.

The condenser C is used for an air conditioning system of a motorvehicle in this embodiment, and includes a right tank 1, a left tank 2,the core part 3 arranged between the right and left tanks 1 and 2, anupper reinforce member 7, and a lower reinforce member 8.

The right tank 1 is formed like a circular cylinder, and is fixed at itstop end portion with an upper cap 4 a for covering its upper opening andat its bottom portion with a lower cap 4 b for covering its loweropening. The right tank 1 is provided at its upper portion with an inletconnector 1 b having a communicating passage 1 a fluidicallycommunicated with a first room R1 formed inside the right tank 1. Theinlet connector 1 b is connected with a not-shown compressor.

The left tank 2 is also formed like a circular cylinder, and is fixed atits top end portion with a left upper cap 4 a for covering its upperopening and at its bottom portion with a lower cap 4 b for covering itslower opening. The left tank 2 is provided at its lower portion with anoutlet connector 2 b having a communicating passage 2 a fluidicallycommunicated with a second room R1 formed inside the left tank 1. Theoutlet connector 2 b is connected with a not-shown expansion valvethrough a not-shown receiver.

The right and left tanks 1 and 2 are fixed with each other by the upperreinforce member 7 connecting the upper portions thereof and by thelower reinforce member 8 connecting the lower portions thereof.

The core part 2 includes a plurality of flat tubes 5 each containing acorrugated inner fin 10, which is shown in FIGS. 3 to 5, and a pluralityof corrugated outer fins 6. The corrugated outer fins 6 and the flattubes 5 are arranged alternately with each other, extending between theright and left tanks 1 and 2. The flat tubes 5 are connected with theright and left tanks 1 and 2 so that right end portions of the flattubes 5 are fluidically communicated with the first room R1 of the righttank 1 and left end portions of the flat tubes 5 are fluidicallyconnected with the second room R2 of the left tank 2.

In the following drawings, a front side direction is indicated as “FW”and a rear side direction is indicated as “RW”.

As shown in FIG. 3, the flat tube 5 is formed from one aluminum sheet bypress forming to have an upper flat wall portion 5 a, a lower flat wallportion 5 b, a front arc wall portion 5 c, rear arc wall portion 5 d,and upper and lower folded wall portions 5 e. The lower wall portion 5 bis arranged in parallel to the upper flat wall portion 5 a, and thefront arc wall portion 5 c is integrally formed with front end portionsof the upper and lower flat wall portions 5 a and 5 b to connecttherewith. The rear arc wall portion 5 d is formed by confronting andbrazing an upper rear arc wall portion and a lower rear arc wall portionwith each other, and the upper and lower folded wall portions 5 e arefaxed and fixed with each other by brazing. The flat tube 5 is formedvertically long and horizontally short, and contains the corrugatedinner fin 10.

As shown in FIGS. 4 and 5, the corrugated inner fin 10 is formed in acorrugated form by press forming to have a plurality of top portions 10a and a plurality of bottom portions 10 b so that the top portions 10 aand the bottom portions 10 b are arranged alternately with each other.The top portions 10 a and the bottom portions 10 b are formed in flat sothat they can fit inner surfaces of the upper wall portion 5 a and thelower wall portions 5 b of the flat tube 5, respectively. Each topportion 10 a is connected with its adjacent bottom portions 10 b byslanted portions 10 c. In addition, the height H1, shown in FIG. 4, ofthe corrugated inner fin 10 is slightly higher than the length H2, shownin FIG. 3, formed between the inner surfaces of the flat tube 5.

Hereinafter, a corrugation is defined by the top portion 10 a and itsboth-adjacent slanted portions 10 c. Therefore, the corrugated inner fin10 is formed to have many corrugations, which project upwardly from thebottom portions 10 b. As shown in FIG. 5 in this embodiment, firstfront-back directional lengths W1 of at least first corrugations N1,which are formed at both end sides of the corrugated inner fin 10, areset to be smaller than second front-back directional lengths W2 of thesecond corrugations N2 arranged between the both-end corrugations N1except front-back directional lengths of third corrugations N3. Thethird corrugations N3 are arranged between the second corrugations N2 tohave the same front-back directional lengths W1 as those of. the firstcorrugations N1. The number of the third corrugations N3 is set to belower than that of the second corrugations N2. In this embodiment, thecorrugated inner fin 10 has the first corrugation N1, two secondcorrugations N2, the third corrugation N3, four second corrugations N2,the third corrugation N3, two second corrugations N2, and the firstcorrugation N1, in these order in a direction from the front side towardthe rear side.

Incidentally, the third corrugations N3 are not indispensable in theinvention.

All parts of the core part C are made of alminum, and one-side parts oftheir connecting parts are provided with a clad layer of brazingmaterial or a brazing sheet for brazing process. Then, by brazing, thetop portions 10 a of the corrugated inner fin 10 are fixed to the innersurface of the upper wall portion 5 a of the flat. tube 5, the bottomportions 10 b of the corrugated inner fin 10 are fixed to the innersurfaces of the lower wall portion 5 b of the flat tube 5, and the upperand lower folded portions 5 e are fixed with each other.

The core part 3 of the first embodiment is manufactured as follows.

The flat tube 5 is press-formed to have the upper and lower wallportions 5 a and 5 b, the front and rear arc wall portions 5 a and 5 d,and the upper and lower folded wall portions 5 e. In this state, theupper and lower wall portions 5 e are separated from each other as shownin FIG. FIG. 9.

FIG. 6 shows how to manufacture the corrugated inner fins 10. Acorrugated inner-fin manufacturing system includes a roll 12, fiveroller devices 13 a to 13 e, a cutter 14, and a not-shown conveyingdevice.

The roll 15 is wound around it with aluminum material 11, to be suppliedto the rollers 15 and 16, including core material made of aluminum,whose inner surface and outer surface are provided with brazing layers.

Each roller device 13 a, 13 b, 13 c, 13 d, and 13 e includes a pair ofupper rotary roll 15 rotatable in a rotation direction RA, shown inFIGS. 6 and 7, and a lower rotary roll 16 rotatable in a rotationdirection RB, shown in FIGS. 6 and 8, opposite to the rotation directionRA.

A shown in FIG. 7, the upper rotary roller 15 has first teeth 15 a andsecond teeth 15 b. The first teeth 15 a are arranged at positionscorresponding to the first corrugations N1 and the third corrugations N3so as to form lower-side surface configurations of the first and thirdcorrugations N1 and N3. The second-teeth 15 b are wider than the firstteeth 5 a, and are arranged at positions corresponding to the secondcorrugations N2 so as to form the lower-side surface configurations ofthe second corrugations N2. As shown in FIG. 8, the lower rotary roller16 has first grooves 16 a and second grooves 16 b. The first grooves 16a are formed to receive the first teeth 15 a so as to form upper-sidesurface configurations of the first corrugations N1 and the thirdcorrugations N3. The second grooves 16 b are formed to receive thesecond teeth 15 b so as to form upper-side surface configurations of thesecond corrugations N2.

The upper rotary roller 15 and the lower rotary roller 16 are set to bevertically apart by a predetermined distance corresponding to athickness of the corrugated inner fin 10, and the aluminum material 11are inserted therebetween and press-formed to be corrugated.

The corrugated aluminum material 11 is conveyed to the cutter 14 movingupward and downward as indicated by an arrow UD, and then is cut intothe corrugated inner fin 10 having a predetermined length.

The corrugated outer fins 6 are manufactured similarly to the corrugatedinner fins 10.

The corrugated inner fin 10 is inserted into the inner space of the flattube 5 as shown in FIGS. 9 and 10, and the upper and lower folded wallportions 5 e are moved to contact with each other.

Then the flat tube 5 containing the corrugated inner fin 10 are pressedfrom above and below by using jigs, not shown, so that the top portions10 a of the corrugated inner fin 10 a and the inner surface of the upperwall portion 5 a of the flat tube 5 are in surely contact with eachother and the bottom portions 10 b of the corrugated inner fin 10 andthe inner surface of the lower wall portion 5 b of the flat tube 5 arein contact with each other.

In this press of the flat tube 5, the flat tube 5 containing thecorrugated inner fin 10 is prevented from causing compressive bucklingand/or being improperly tilted, because the both end portions of theinner fin 10 have the first corrugations N1, smaller in the front-backdirectional length than the second corrugations N2, to increase itscompressive strength at the both end portions thereof, although the bothend portions of the flat tube containing the conventional corrugatedinner fin are weak in compressive strength. The third corrugations N3,also in the front-back directional length than the second corrugationsN2, increases the compressive strength at the intermediate portion ofthe flat tube 5, while the third corrugations N3 are not indispensable.

The flat tube 5, containing the corrugated inner fin 10, with the jigsis brought into a not-shown heating furnace to be heated to braze thecorrugated inner fin 10 and the flat tube 5 with each other. After thisheat treatment, all parts of the condenser C, including the right andleft tanks 1 and 2, the upper and lower reinforce members 7 and 8, thecorrugated outer fins 6, the flat tubes 5 with the corrugated inner fins10, the inlet connector 1 b and the outlet connector 2 b, are temporallyassembled with one another, and then the temporally assembled parts arebrought into another heat furnace and is be brazed to integrally formthe condenser C.

Incidentally, the heat treatment of the flat tubes 5 and the heattreatment of the all parts are independently performed in the firstembodiment, while they may be brazed at the same time.

The condenser C is mounted on a front portion of the motor vehicle bodyand is fluidically connected with parts of the air conditioning system.

The operation of the condenser C having the corrugated inner fins 10 ofthe first embodiment will be described.

The heat transfer medium having a temperature of approximately 70° C. isled from the compressor to the first room R1 of the right tank 1 throughthe communicating passage 1 a of the inlet connector 1 b and a not-shownpipe, and flow through the flat tubes t toward the left tank 2, beingcooled down to a temperature of approximately 40° C. by the air causedwhen the motor vehicle and/or the air generated by a not-shown motorfan. The heat transfer medium flown into the left tank 2 is dischargedtoward the evaporator through the commnunicating passage 2 a of theoutlet connector 2 b and a not-shown pipe.

In this heat transfer, the corrugated inner fins 10 improve a heattransfer efficiency of the condenser C by their large heat-transferarea. In addition, the corrugated inner fins 10 are set thinner inthickness, and accordingly decrease the drag force caused when the heattransfer medium flows in the flat tubes 5.

The core structure of the first embodiment has the following advantages.

The corrugated inner fin 10 has the first corrugations N1, which aresmaller in the front-back directional length than the secondcorrugations N2 and are arranged at the both end portion of thecorrugated inner fin 10. Therefore, the flat tube 5 containing the innerfin 10 is improved in compressive strength especially at its both endportions, thereby being prevented from causing the compressive bucklingand/or improperly tilted during the press working of the flat tube 5.This can provide sure and firm brazing thereof, and allows thecorrugated inner fin 10 to be thinner than the conventional corrugatedinner fins. Accordingly, the drag force can be decreased, therebyimproving the heat transfer efficiency of the condenser C.

A core structure, of a heat exchanger, of a second embodiment accordingto the present invention will be described with reference to theaccompanying drawings.

As shown in FIGS. 11 and 12, a corrugated inner fin 20 is inserted intoa flat tube 5 and fixed to each other by using brazing, similarly tothose of the first embodiment.

The corrugated inner fin 20 has first corrugations N4 at both endportions of the corrugated inner fin 20 and second corrugations N5arranged at a front side thereof, and third corrugations N6 arranged atrear side thereof.

The first and third corrugations N4 and N6 are set to have a front-backdirectional length W1 smaller than a front-back directional length W2 ofthe second corrugations N5.

The other parts and how to manufacture a condenser with a core structurethe second embodiment are similarly to those of the first embodiment,and their descriptions are omitted.

Therefore, the corrugated inner fin 20 can increase the compressivestrength of the flat tube 5 containing the corrugated inner fin 20,especially at its both end portions.

In addition, a heat transfer efficiency between heat transfer medium andthe air through the corrugated inner fin 10 when a flow amount of theheat transfer medium is small, because more amount of the heat transfermedium flows through a front portion of the flat tube 5, which causesdrag force smaller than that through a rear portion thereof.

Further, the second corrugations N5 are arranged at the front side ofthe corrugated inner fin 20, so that a strength at the front sidebecomes weaker than a strength at the rear side. This can absorb animpact force acting from an exterior of the condenser C, for example,when a jumping stone hits the flat tube 5 during the motor vehiclerunning.

Incidentally, in the second embodiment, the number of the thirdcorrugations located at a front side of the corrugated inner fin arelarger than the number of the third corrugations located at a rear sideof the corrugated inner fins, where the number of the rear-side thirdcorrugations may be zero or more.

A core structure, of a heat exchanger, of a third embodiment accordingto the present invention will be described with reference to theaccompanying drawing.

As shown in FIG. 13, a corrugated inner fin 30, used in a flat tube ofthe core structure of the third embodiment, has at least two firstcorrugations N1 at each end portion of the corrugated inner fin 30.

This can further increase strength at the both end portion of the flattube containing the corrugated inner fin 30.

While there have been particularly shown and described with reference topreferred embodiments thereof, it will be understood that variousmodifications may be made therein, and it is intended to cover in theappended claims all such modifications as fall within the true spiritand scope of the invention.

In the embodiments, the condenser C is used as the heat exchanger of thepresent invention, while it may employ an oil cooler and the like, usingthe corrugated inner fins 10, 20, or 30.

The first corrugations, the second corrugations, and the thirdcorrugation are arranged symmetrically with respect to the front-backdirection of the corrugated inner fin.

The entire contents of Japanese Patent Application No. 2005-373843 filedDec. 27, 2005 are incorporated herein by reference.

1. A core structure of a heat exchanger where a core part is arrangedbetween a pair of tanks, the core structure comprising: a plurality offlat tubes having an upper wall portion and a lower wall portion; and aplurality of corrugated inner fins formed in a corrugated shape so thateach corrugated inner fin has top portions for being fixed to an innersurface of the upper wall portion, bottom portions for being fixed to aninner surface of the lower wall portion, and slanted portions forconnecting the top portion with adjacent bottom portions thereof, thecorrugated inner fin having first corrugations located at both end sidesof the corrugated inner fin and second corrugations located between thefirst corrugations, where each of the first and the second corrugationshas the top portion and the adjacent slanted portions and project fromthe bottom portions, wherein the first corrugations are set to besmaller in a front-back directional length of the corrugated inner finthan a front-back directional length of the second corrugations.
 2. Thecore structure according to claim 1, wherein the corrugated inner finhas at least one third corrugation which is smaller in the front-backdirectional length than the second corrugations and arranged between thesecond corrugations.
 3. The core structure according to claim 2, whereinthe number of the third corrugations located at a front side of thecorrugated inner fin are larger than the number of the thirdcorrugations located at a rear side of the corrugated inner fin.
 4. Thecore structure according to claim 2, wherein the first corrugations, thesecond corrugations, and the third corrugation are arrangedsymmetrically with respect to the front-back direction of the corrugatedinner fin.